1. Field of the Invention
The present disclosure relates to an interval guarantee member used for an image forming apparatus, a process cartridge and a developing apparatus having the interval guarantee member.
The term the image forming apparatus used here includes, for example, an electrophotographic image forming apparatus configured to form images on recording media by using an electrophotographic image forming system. Examples of the electrophotographic image forming apparatus includes, for example, electrophotographic copying machines, electrophotographic printers (for example, laser beam printers, LED printers), facsimile apparatus, and word processors.
The term, the interval guarantee member is a member configured to maintain the distance between an image bearing member and a developer bearing member used for the image forming apparatus constant.
2. Description of the Related Art
In the related art, an electrophotographic image forming apparatus such as an electrophotographic copying machine or a laser beam printer selectively exposes an electrophotographic photosensitive member (image bearing member), which is uniformly charged by a charging device, forms a latent image, and makes the latent image visible by a developing device with toner. Image recording is performed by transferring and fixing a toner image on the recording medium. Toner remaining on the electrophotographic photosensitive member after the transfer is cleaned and removed by a cleaning device.
The image forming apparatus having the configuration as described above is provided with an interval guarantee member as a device for controlling the interval between a photosensitive drum and a developing roller constant.
As an example of the interval guarantee member composed of a member, a method of interposing a roll-type member between the photosensitive drum and the developing roller by an urging force of a spring or the like, and defining the interval between the photosensitive drum and the developing roller constant by the thickness of a roller is known. Here, the roller maintains the interval between the photosensitive drum and the developing roller while being rotated by the rotation of one of the photosensitive drum and the developing roller, which rotate so that peripheral surfaces thereof move in the same direction at an opposing portion. Therefore, in order to suppress variations of the clearance in this device caused by the rotation of the roller, the variations in the thickness need to be suppressed so as to obtain the roller having a uniform thickness over the entire circumference.
In contrast, a fixed interval guarantee member which is not rotated in association with the photosensitive drum or the developing roller is also proposed (refer to Japanese Patent Laid-Open No. 5-27571). In Japanese Patent Laid-Open No. 5-27571, a sheet-type interval retaining member is fixed in a state of being interposed between the photosensitive drum and the developer roller. As an advantage of this system is that variations of the interval caused by the rotation of the roller is reduced because a contact portion on the side of the interval guarantee member is always constant with respect to the rotation of the roller. In this case, in order to prevent the sheet-type interval guarantee member from being rotated in association with the photosensitive drum and the developing roller, one end of the sheet, which is the interval guarantee member, is fixed to the image forming apparatus to restrict the movement of the interval guarantee member. Therefore, an adhesive agent or double-faced tape as a fixing device needs to be provided separately from the sheet, which is the interval guarantee member.